Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

With no annotations supplied, the description carries the full burden and does meaningful work: it establishes read-only semantics ("Retrieves"), discloses the authentication requirement and that the x-api-key header is sent automatically, and warns that pricing is scoped to one adult. It omits what happens for a nonexistent or invalid ID, which is the main remaining behavioral gap.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Two sentences, no filler, with the core lookup behavior and return scope front-loaded ahead of the authentication note. Every clause earns its place.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a one-parameter read tool with no output schema and no nested structures, the definition covers purpose, return shape, and auth. Only the not-found/error behavior is unaddressed, a minor gap at this complexity level.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100% and the single id parameter is already documented as a positive numeric itinerary ID. The description's "numeric ID" restates the schema rather than adding new meaning; baseline 3 applies when the schema does the lifting.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb and resource ("Retrieves a single itinerary by its numeric ID") plus the depth of data returned (day-by-day detail, pricing for one adult). The contrast with the sibling list_itineraries is only implied by "single," not stated explicitly, so it falls just short of the top mark.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description conveys that this is the single-record lookup, which implies when to reach for it, but it never explicitly says to use list_itineraries for enumeration or search_flights for alternatives. No exclusions or prerequisites beyond the API key are given.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.